Himself was his greatest rival. If he had as much consistency as Federer, he would have won even more than 14 majors. Also, if he enjoyed the sport more, he would have played longer and won even more.

I somewhat agree with you. I think it is unexplainable to win a major tournament and be fit and healthy and then stop playing. Sure he could have taken 6 months off and came back refreshed. It will also explain why he was playing so many exhibitions against younger men between 2006 and 2011. He won't say but I think deep down he must feel he made a mistake retiring at that stage.